Mems-based variable optical attenuator array

ABSTRACT

The present disclosure provides a MEMS -based variable optical attenuator (VOA) array, sequentially including an optical fiber array, a micro-lens array, and a MEMS-based micro-reflector array to form a VOA array having several optical attenuation units. The MEMS-based micro-reflectors can change the propagation direction of a beam, causing a misalignment coupling loss to the beam and thereby achieving optical attenuation, with a broad range of dynamic attenuation, low polarization dependent loss and wavelength dependent loss, good repeatability, short response time (at the millisecond level), etc. Arrayed device elements are used as assembly units of the present disclosure, and the assembly of arrayed elements facilitates tuning in batches. Accordingly, automation levels are improved, and the production costs are reduced.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No.202010056833.5 filed on Jan. 16, 2020, the content of which is reliedupon and incorporated herein by reference in its entirety.

TECHNICAL FIELD

The disclosure relates generally to the field of optical fibercommunications, in particular to a MEMS-based variable opticalattenuator array.

BACKGROUND

Variable Optical Attenuators (VOAs) are a type of important opticalpassive devices used in optical fiber communication systems. The VOAdevice regulates an intensity of optical signals in real time byattenuating an optical power. In one type of application, the VOA devicecan be used in an ultra-long distance Dense Wavelength DivisionMultiplexing (DWDM) system, where environmental factors can causechanges to optical power in a channel In such a system, the VOA devicecan perform instant signal compensation based on its own sensitivity andreliability, thereby ensuring the accuracy and authenticity ofinformation transmission.

In other applications, the VOA device can be readily integrated withother optical devices, such as an Erbium Doped Optical Fiber Amplifier(EDFA), through optical fiber connections. The VOA device can performgain flattening. Additionally, the VOA device with the other opticaldevices can form modular products with more complex functions, whichadvances the development of high-order photoelectric modules. Inaddition, the VOA device may also be directly used for overloadprotection of optical receivers, as well as for measurement andcalibration of instrumentation, such as optical power meters. Overall,the VOA devices have become one of the optical passive devices mostextensively used in optical communication systems, and the hugeapplication market has strongly advanced the manufacturing anddevelopment of VOA devices.

At present, there are many types of manufacturing technologies forrealizing VOA devices, including conventional mechanical technologies,planar optical waveguide technologies, liquid crystal technologies,magneto-optical technologies, micro-electromechanical systems (MEMS),and the like. Of these, MEMS-based VOA devices have been used in a largenumber of products and large-scale applications because the MEMS-basedVOA devices have advantages of small mechanical dimensions, goodperformance stability, easiness for integration, and suitability forlarge-scale production, etc. Along with the development of DWDM systemsand the tremendous potential market demands for Reconfigurable OpticalAdd/Drop Multiplexer (ROADM) technology that can be obtained throughflexible upgrade, miniaturization and multi-channel integration of a VOAdevice may become one of the targets and requirements of next-stepdevelopment of optical transmission systems.

SUMMARY

Directed towards meeting the above-described technical requirements, thepresent disclosure provides a MEMS-based variable optical attenuator(VOA) array having simplified control principles and fast responsespeed. Additionally, the construction of the MEMS-based VOA array allowthe array to readily produced using automated production.

Directed towards the above-described goals, the present disclosureincludes the following technical solutions.

As disclosed herein, a MEMS-based variable optical attenuator array,sequentially includes an optical fiber array, a micro-lens array, and aMEMS-based micro-reflector array to form a VOA array having severaloptical attenuation units.

In some examples, the optical fiber array includes optical fibersarranged in pairs, with each pair of optical fibers including anincoming optical fiber and an outgoing optical fiber arrangedcorrespondingly. Lenses in the micro-lens array can be distributed atequal distances with a high precision. A distance between adjacentlenses can be equal to a distance between adjacent pairs of opticalfibers. Reflectors in the MEMS-based micro-reflector array can bearranged at equal or same distances and can be arranged coaxially withrespect to the lenses in the micro-lens array and the pairs of opticalfibers. The reflectors can change the propagation direction of lightbeams, causing a misalignment coupling loss to the beams and therebyachieving attenuation of specific incident light.

In certain examples, the optical fiber array is a bare optical fiberarray or an optical fiber pigtail array, such as a dual optical fiberpigtail array.

In another example, micro-lenses included in the micro-lens array arecylindrical lenses, which can be G-lenses or C-lenses.

In other examples, the micro-lens array is a stamped piece, asilicon-based etched piece, or an assembly obtained by using orincluding a positioning device.

In some examples, the variable optical attenuator array has theadvantage of being tuned in batches and finally assembled inside anencapsulation structure.

In certain examples, the encapsulation structure includes an outerencapsulation tube and a base. One end of the outer encapsulation tubeis integrally connected to the base, and another end of the outerencapsulation tube has a through hole for incoming optical fibers andoutgoing optical fibers to pass through. The outside of the base isfixed with several groups of PINs, each group of PINs are connected to aMEMS chip in the MEMS-based micro-reflector array and used for providinga drive voltage for the MEMS chip, thereby changing angles of reflectivelenses.

In another example, a buffer gasket is provided between the base andMEMS chip, and the buffer gasket provides protection against vibrationand shock for the MEMS-based micro-reflector array.

In other examples, gold-tin soldering, electric resistance welding, oradhesive bonding is used to connect one end of the outer encapsulationtube to the base so as to assemble the two into one integral piece.

In some examples, the through hole on another end of the outerencapsulation tube is encapsulated with adhesive.

By using the above-described technology, the present disclosure providesthe following technical effects.

In some examples of the present disclosure, the VOA array includes acombination of a MEMS-based micro-reflector and a collimating lens torealize controllable attenuation modulation of optical signals, havingbroad range of dynamic attenuation, low Polarization Dependent Loss(PDL) and Wavelength Dependent Loss (WDL), good repeatability, shortresponse time (at the millisecond level), etc.

In certain examples of the present disclosure, the VOA arraysequentially includes a chip array, a lens array, and an optical fiberarray distributed at equal distances, e.g., with a high precision, whichcontains a relatively small number of types of device elements and arelatively small number of parameters to be tuned during the assembly.The assembly of arrayed elements may facilitate tuning in batches.Accordingly, automation in the production of the arrays may be improved,and the production costs may be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be further described in detail below withreference to embodiments and accompanying drawings in which:

FIG. 1A illustrates a schematic diagram of an example individual opticalattenuation unit according to the present disclosure from a side view;

FIG. 1B illustrates the example individual optical attenuation unit ofFIG. 1A from a top view;

FIG. 2 illustrates a schematic structural diagram of a MEMS-basedvariable optical attenuator (VOA) array according to an embodiment ofthe present disclosure;

FIG. 3 illustrates a schematic structural diagram of an examplemicro-lens array according to various embodiments of the presentdisclosure;

FIG. 4 illustrates a schematic structural diagram of another MEMS-basedVOA array according to another embodiment of the present disclosure;

FIG. 5 illustrates a schematic diagram of yet another MEMS-based VOAarray including an encapsulation structure according to variousembodiments of the present disclosure; and

FIG. 6 illustrate a flowchart of an example method of assembling avariable optical attenuator (VOA) device.

The numerals in the drawings representing the correspondingrelationships include: 10—incoming optical fiber, 20—outgoing opticalfiber, 30—optical fiber positioning device, 40—lens, 50—MEMS-basedmicro-reflector, 60—optical fiber array, 70—micro-lens array,80—MEMS-based micro-reflector array, 90—dual optical fiber pigtailarray, 130—PIN, 125—buffer gasket, 124—base, 122—outer encapsulationtube, 129 through-hole having adhesive.

DETAILED DESCRIPTION

FIGS. 1A-1B illustrate schematic diagrams from a side view and a topview of an example individual optical attenuation unit 110 for use in anexample micro-electromechanical system (MEMS)-based variable opticalattenuator (VOA) array of the present disclosure. As shown, an incomingoptical fiber 10 and an outgoing optical fiber 20 are fixed on anoptical fiber positioning device 30. During operation, an incomingoptical signal enters a lens 40 via the incoming optical fiber 10. Theoriginally divergent optical signal is converted, after passing throughthe lens 40, to a collimated light beam that irradiates to a reflectionregion of a MEMS-based micro-reflector 50. When there is no drivevoltage to the reflector 50, an end surface 52 of the MEMS-basedmicro-reflector 50 is essentially parallel to the end surfaces of theoptical fibers 10, 20. In this case, the incoming light beam isreflected by the MEMS-based micro-reflector 50, and further outputted ina coupled way via the outgoing optical fiber 20. Accordingly, an energygap or energy difference between the incoming light and the outgoinglight is given directly by the attenuation inherent to the attenuationdevice unit 110 itself.

When a certain drive voltage is provided to a chip of the MEMS-basedmicro-reflector 50, the reflection surface (or the end surface) 52 ofthe MEMS-based micro-reflector 50 rotates by a given angle A1. As willbe appreciated, the drive voltage can be provided from any suitabledrive component (not shown) external to the chip of the MEMS-basedmicro-reflector 50. The given angle A1 can be a tiny angle, which, asshown in FIG. 1B, drives or causes the reflected light beam to undergo asynchronous shift 101. In this way, the angling of the reflector 50relative to the coaxially arranged lens 72 and optical pairs 10, 20changes a propagation direction of the beam, causing a misalignmentcoupling loss to the beam and thereby regulating the attenuation ofspecific incident light. Thus, this shift 101 leads to a mismatchbetween a first mode field of the reflected light beam transmitted to anend surface 22 of the outgoing optical fiber 20 and a second mode fieldof the coupled outgoing optical fiber 20. The mismatch causes anattenuation of the reflected light beam to a certain degree. As theapplied drive voltage changes, the given angle A1 changes, and theattenuation changes correspondingly and is continuously variable.

As disclosed below, several of such attenuation units 110 can be usedtogether in MEMS-based variable optical attenuator (VOA) array 100according to the present disclosure. For example, FIG. 2 is a schematicstructural diagram of a MEMS-based variable optical attenuator (VOA)array 100 according to an embodiment of the present disclosure. Asshown, the VOA array 100 sequentially includes an optical fiber array60, a micro-lens array 70, and a MEMS-based micro-reflector array 80,which may be sequentially assembled to form an array 100 having aplurality of optical attenuation units 110.

Specifically, the MEMS-based VOA array 100 includes several opticalattenuation units 110, which may be in an arrangement of a single row ormay be in a multi-layer stacked arrangement. For example, in anarrangement of a single row, the optical attenuation units 110 may bearranged in one row and at least two columns, such as 1 by 2, 1 by 4, 1by 8, 1 by 12, etc. In an arrangement of a single column, the opticalattenuation units 110 may be arranged in at least two rows and in onecolumn, such as 2 by 1, 4 by 1, 8 by 1, 12 by 1, etc. In a multi-layerstacked arrangement, the optical attenuation units 110 may be arrangedin at least two rows and at least two columns, such as 2 by 2, 4 by 4, 2by 4, 8 by 3, etc. These and other configurations for the array 100 canbe used.

In some examples, the optical fibers 10, 20 in the optical fiber array60 are bare optical fibers and are distributed in pairs. Each pair ofoptical fibers 10, 20 sequentially corresponds to the incoming opticalfiber 10 and the outgoing optical fiber 20 for a single opticalattenuation unit 110.

In some examples, lenses 72 in the micro-lens array 70 are distributedat equal distances, and a distance D7 between adjacent lenses 72 isequal to a distance D6 between adjacent optical-fibers pairs in theoptical fiber array 60. Accordingly, each micro-lens 72 is coaxial witha corresponding pair of optical fibers 10, 20, which are used forachieving precise transmission of the incoming light and the outgoinglight. In some examples, the micro-lenses 72 are cylindrical lenses,which may be G-lenses or C-lenses.

By way of example, FIG. 3 illustrates a schematic structural diagram ofthe micro-lens array 70. The micro-lens array 70 includes multiplelenses 72 positioned in a positioning structure 74, which allows forhigh precision placement of the lenses 72. The positioning structure 74of the micro-lens array 70 may be a stamped piece or structure, asilicon-based etched piece or structure, or an assembly obtained byusing or including one more V-shaped grooves or other positioningdevices.

As further shown in FIG. 2 , the MEMS-based micro-reflector array 80includes MEMS-based micro-reflectors 82, each including or being a MEMSchip. For example, each MEMS-based micro-reflector 82 may include or maybe a MEMS chip, and surfaces of the MEMS chip may be used as reflectionsurfaces of the MEMS-based micro-reflectors 82. Each chip is used forone of the MEMS-based micro-reflectors 82 contained in the MEMS-basedmicro-reflector array 80. The MEMS chip of the MEMS-basedmicro-reflector 82 may include an independent drive circuit, which mayprovide differential modulation of a multi-channel communication networkdriven by different voltages. The micro-lens array 70 may preciselytransmit N beams incoming from the optical fiber array 60 to centralreflection regions of MEMS-based micro-reflectors 82, e.g., centralreflection regions of the MEMS chips of MEMS-based micro-reflectors 82.In turn, the MEMS-based micro-reflectors 82 accurately transmit thereflected beams to corresponding outgoing optical fibers 20 according topreset angles, thereby reducing beam crosstalk and ensuring mutualindependence among a plurality of device units 110 in the array 100. Insome examples, N may be a positive integer.

FIG. 4 illustrates a schematic structural diagram of another MEMS-basedVOA array 100 according to another embodiment of the present disclosure.As shown, the variable VOA array 100, e.g., a complete variable VOA,includes a dual optical fiber pigtail array 90 (also referred to as a“dual optical fiber head array”), a micro-lens array 70, and aMEMS-based micro-reflector array 80 to form a plurality of opticalattenuation units 110. A dual optical fiber pigtail 92, also referred toas a “dual optical fiber head,” includes a glass structure 94 and anincoming optical fiber 10 and an outgoing optical fiber 20, and theglass structure 94 includes a pair of holes (e.g., capillaries) for theincoming optical fiber 10 and the outgoing optical fiber 20 to passtherethrough and for positioning the incoming optical fiber 10 and theoutgoing optical fiber 20. The light path of the example of FIG. 4 isthe same as or similar to the light path of the above-described exampleof FIG. 2 . In contrast to the array 100 of FIG. 2 , the optical fibersin the dual optical fiber pigtail array 90 of FIG. 4 are an array ofdual optical fiber pigtails 92, rather than bare optical fibers in theexample of FIG. 2 .

In some embodiments of the present disclosure, a chip array, amicro-lens array, and an optical fiber array distributed coaxially andat equal distances may be included, e.g., sequentially included. Forexamples, an array of chips, an array of micro-lenses, and an array ofoptical fibers may be distributed coaxially and at equal distances, andmay be included in a device consistent with the present disclosure.Accordingly, a MEMS-based VOA array 100 as disclosed herein may containa relatively few types of device elements and may have a relatively fewparameters that need to be tuned or debugged during the assembly of thearray 100. Further, the assembly of arrayed elements may facilitatedevice-tuning in batches. Accordingly, automation in the assembly of thearrays 110 may be increased, and the production costs may be reduced.

An air-tight encapsulation may be used for fabricating a VOA array 100of the present disclosure, such as the VOA array 100 in FIG. 4 . In allembodiments, or alternatively in one embodiment, or alternatively in atleast one embodiments of the present disclosure, encapsulation in themode shown in the example of FIG. 5 is performed. In the presentdisclosure, the VOA array 100 may be tuned in batches and assembledinside encapsulation structures.

The component arrays, such as the dual optical fiber pigtail array 90,the micro-lens array 70, and the MEMS-based micro-reflector array 80,can be assembled or tuned in batches, without the need to assembleseparate components (such as individual lens, individual optical fiberpigtails, individual MEMS-based micro-reflector) one by one.Accordingly, the assembling process may be simplified.

As shown in FIG. 5 , the encapsulation structure 120 includes an outerencapsulation tube or housing 122 and a base 124. One end 126 of theouter encapsulation housing 122 is integrally connected with the base124, and another end 128 of the outer encapsulation housing 122 isformed with a through-hole 129 for incoming optical fibers 10 andoutgoing optical fibers 20 to pass through. The outside of the base 124is fixed with several groups of PINs 130, and each group of PINs 130 areconnected to a MEMS chip of a MEMS-based micro-reflector 82 in theMEMS-based micro-reflector array 80 via gold wires and used forproviding a drive voltage for the MEMS chip of the MEMS-basedmicro-reflector 82, so as to achieve angle changes of the reflectiveMEMS-based micro-reflector 82. A material of the base 124 may includeceramic or other insulative materials. A buffer gasket 125 is providedon an inner side of the base 124, and the buffer gasket 125 providesprotection against vibration and shock for the MEMS-basedmicro-reflector array 80. Gold-tin soldering, electric resistancewelding, or adhesive bonding may be used to connect (or couple) one end126 of the outer encapsulation housing 122 to the base 124 to assemblethe two integrally into one piece. The through-hole 129 on another end128 of the outer encapsulation housing 122 is encapsulated withadhesive.

In some examples, distances between adjacent optical attenuation units110 in a MEMS-based VOA array 100 of the present disclosure are thesame, along a row direction and/or a column direction. This uniformarrangement is preferred to facilitate assembly of the MEMS-based VOAarray 100 during manufacture. In other examples, some or all of thedistances between adjacent optical attenuation units 110 in a MEMS-basedVOA array 100 of the present disclosure can be different, and in eachindividual optical attenuation unit 110, the pair of optical fibers 10,20 or the dual optical fiber pigtail is aligned coaxially with themicro-lens 72 and the micro-reflector 82.

FIG. 6 illustrate a flowchart of an example method 600 of assembling avariable optical attenuator (VOA) device to attenuate optical signals.The method 600 is described below with reference to FIGS. 5 and 6 .

At S601, the reflector array 80 is coupled to the base 124 by bondingthe reflector array 80 to the base 124. In some examples, the reflectorarray 80 has reflectors, each including or being amicro-electromechanical systems (MEMS) chip, and each MEMS chip isconfigured to position or control a respective reflector. In someexamples, a buffer gasket may be positioned between the reflector array80 and the base 124, by bonding the buffer gasket 125 to the base 124,and further bonding the reflector array 80 to the buffer gasket 125. Insome examples, each of the MEMS chips may be electrically connected to apin disposed in the base 124.

At S602, the lens array 70 is positioned adjacent the reflector array 80and coupled to the base 124 by bonding the lens array 70 to the base124. For example, the lens array 80 may be aligned with the reflectorarray 80, and the lens array 80 may be bonded to a shoulder of the base124. The lens array 70 may have a plurality of lenses 72 each disposedin optical communication with a respective one of the reflector 82.

At S603, the optical fiber array is tuned, and further coupled to thelens array 70 by bonding. For examples, the optical fiber array (e.g., adual optical fiber pigtail array 90) has a plurality of optical pairseach having an input and an output, and can be positioned adjacent thelens array 70, and can be tuned in a batch. In some examples, theoptical fibers of the optical fiber array can be tuned together, e.g.,so as to align the optical fiber array with the lens array 70. With theoptical fiber array tuned, the optical fiber array may be bonded to thelens array 70 by, e.g., providing adhesive on sides of the optical fiberarray and the lens array 70.

At S604, the reflector array 80, the lens array 70, and the opticalfiber array are encapsulated. The reflector array 80, the lens array 70,and the optical fiber array may be encapsulated by connecting thehousing 122 to the base 124 and by filling the through-hole 129 withadhesive.

In some examples, the lens array 70 may be constructed by installinglenses 72 into a stamped structure, a silicon-based etched structure, ora positioning device. In some examples, the optical fiber array 70 maybe constructed by positioning pairs of bare optical fibers in apositioning device or positioning optical fibers in pairs of capillariesof a glass structure.

Implementations of the present invention have been described above withreference to the accompanying drawings, but the present invention is notlimited to the above-described specific embodiments, which areillustrative, rather than limiting the present invention. Those ofordinary skills in the art should understand that they may still modifythe technical solutions recited in the above-described embodiments orperform equivalent substitutions on part or all of the technicalfeatures thereof. Such modifications or substitutions do not cause theessence of corresponding technical solutions to depart from the scope ofthe technical solutions in the embodiments of the present invention, butshall all fall within the scope of the present invention.

The term “couple” or similar expression means either an indirect ordirect connection. If device A is coupled to device B, that connectionmay be through a direct connection or through an indirect connection viaother devices and connections.

The present disclosure may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive.

1-20. (canceled)
 21. A variable optical attenuator (VOA) device,comprising: a reflector array having a plurality of reflectors; a lensarray adjacent the reflector array, the lens array having a plurality oflenses installed in a lens positioning structure, each of the lensesdisposed in optical communication with a respective one of thereflectors; and a fiber positioning device adjacent the lens array, thefiber positioning device having a plurality of optical pairs of anoptical fiber array positioned therein.
 22. The VOA device of claim 21,wherein each of the optical pairs have an input and an output and areconfigured to communicate optical signals with a respective one of thelenses of the lens array.
 23. The VOA device of claim 22, wherein eachof the plurality of reflectors is configured to attenuate the opticalsignals from the input to the output of the respective optical pair. 24.The VOA device of claim 21, wherein each of the reflectors having amicro-electromechanical systems (MEMS) chip configured to position arespective one of the plurality of reflectors.
 25. The VOA device ofclaim 21, wherein each respective optical pair, lens, and reflector aredisposed coaxial with one another.
 26. The VOA device of claim 21,wherein each of the optical pairs of the optical fiber array comprisesone of (i) an incoming optical fiber and an outgoing optical fiber, (ii)a pair of bare optical fibers; and (iii) an optical fiber pigtail havingthe optical pairs passing through a pair of capillaries.
 27. The VOAdevice of claim 21, wherein each of the plurality of lenses of the lensarray comprises a cylindrical micro-lens.
 28. The VOA device of claim21, wherein the lens positioning structure comprises one of (i) astamped structure having the plurality of lenses installed therein, (ii)a silicon-based etched structure having the plurality of lensesinstalled therein, and (iii) a lens positioning device having theplurality of lenses installed therein.
 29. The VOA device of claim 21,comprising a base supporting the reflector array, the lens array, andthe fiber positioning device.
 30. The VOA device of claim 29, whereinthe reflector array is bonded adjacent a surface of the base, andwherein the lens array is bonded to a shoulder of the base offset fromthe surface.
 31. The VOA device of claim 29, comprising a housingextending from the base and enclosing the fiber positioning device, thelens array, and the reflector array therein.
 32. The VOA device of claim31, wherein the housing comprises a through-hole opposite the base forpassage of a portion of the optical fiber array into the housing. 33.The VOA device of claim 31, wherein the plurality of optical pairs andthe respective reflectors are arranged in one or more columns and in oneor more rows.
 34. An optical system, comprising: an array of reflectors;an array of lenses adjacent the array of reflectors; and an array ofoptical fibers adjacent to the array of lenses, wherein the lenses ofthe array of lenses are positioned in a lens positioning structure inoptical communication with one of the reflectors of the array ofreflectors, and wherein the array of optical fibers includes a pluralityof optical pairs positioned in a fiber positioning device.
 35. Theoptical system of claim 34, wherein each respective optical pair, lens,and reflector are disposed coaxial with one another.
 36. The opticalsystem of claim 34, wherein the plurality of optical pairs andrespective reflectors of the array of reflectors are arranged in one ormore columns and in one or more rows.
 37. The optical system of claim34, wherein each of the optical pairs of the array of optical fiberscomprises one of (i) an incoming optical fiber and an outgoing opticalfiber, (ii) a pair of bare optical fibers; and (iii) an optical fiberpigtail having the optical pairs passing through a pair of capillaries.38. The optical system of claim 34, wherein each of the reflectors ofthe array of reflectors comprises a micro-electromechanical systems(MEMS) chip configured to position the reflector.
 39. The optical systemof claim 34, wherein each lens of the array of lenses array comprises acylindrical micro-lens.
 40. The optical system of claim 34, comprising:a base supporting the array of reflectors array, the array of lenses,and the fiber positioning device; and a housing extending from the baseand enclosing the fiber positioning device, the array of lenses, and thearray of reflectors, wherein the housing comprises a through-holeopposite the base for passage of a portion of the array of opticalfibers into the housing.